Synthesis and electrochemical characterization of sol–gel-derived RuO2/carbon nanotube composites

Ruthenium oxide was coated on multiwalled carbon nanotubes (MWCNTs) to obtain nanocomposite electrode which has a good response to the pH. To synthesize this electrode, gold and cobalt were coated on a stainless steel 304 substrates, respectively, and then, vertically aligned carbon nanotubes were grown on the prepared substrates by chemical vapor deposition. Gold reduced activity of the stainless steel, while cobalt served as a catalyst for growth of the carbon nanotube. Ruthenium oxide was then coated on MWCNTs via sol–gel method. At last, different techniques were used to characterize the properties of synthesized electrode including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction, and cyclic voltammetry. SEM results showed that the length of the carbon nanotubes varied with reaction time, and in this research, it was maintained around 9 μm with a diameter about 100 nm. Electrochemical analysis revealed that optimum sol concentration and heat treatment temperature to meet the best pH sensing response were 0.1 M RuCl₃ sol and 200 °C, respectively. Moreover, the obtained electrode represented a linear and near-Nernstian response (about ?63 mV/pH) throughout the whole pH range (2–12) of Britton–Robinson buffer solutions.     

Synthesis,characterization, and visible light–induced photocatalytic evaluation of WO3/NaNbO3 composites for the degradation of 2,4-D herbicide

In this research study, WO₃/NaNbO₃-coupled photocatalysts were synthesized at three WO₃ mass ratios (15, 85, and 95 wt%) and characterized. These composites were characterized via X-ray powder diffraction, N₂ physisorption, UV–Vis diffuse reflectance spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy, and photoluminescence techniques. For comparison, bare WO₃ and NaNbO₃ were also synthesized and characterized. 2,4-Dichlorophenoxyacetic acid (2,4-D) was degraded under visible light to evaluate its photocatalytic performance. The WO₃ (95 wt%)/NaNbO₃ composite showed higher photocatalytic activity than pure WO₃ and NaNbO₃ and even than the 15 and 85 wt% coupled materials; thus, the combination with the highest ratio of WO₃ with respect to NaNbO₃ showed increased photocatalytic activity compared with the bare materials.     

Synthesis,characterization, and hydrolytic degradation of polylactide/poly(ϵ-caprolactone)/nano-silica composites

Poly(lactic acid) (PLA)/poly(?-caprolactone) (PCL)/nano-silica composite degradable films were prepared by a solvent casting method. SEM results showed that the nano-silica particles were dispersed uniformly in the PLA/PCL matrix. TGA results indicated that the thermal decomposition temperature rose with the increase of nano-silica content. The tensile strength of the composites was enhanced with the increase of nano-silica content up to 2%. The tensile strength increased with the silica content and reached its maximum (22.51 Mpa). The improvement in the water uptake ratio in the PLA/PCL/silica nanocomposites may be attributable to the presence of silica nanoparticles in the PLA/PCL matrix. After 15 weeks total processing time for the solution of alkaline and phosphate buffer, the performances of 16.23% and 3.65% for degradation.     

Synthesis,characterization and photocatalytic properties of Mg1−xZnxAl2O4 spinel nanoparticles

Mg_1−xZn_xAl₂O₄ spinel nanoparticles with x = 0, 0.05, 0.10, 0.15 and 0.20 were prepared via the chemical coprecipitation method. The obtained samples were characterised by thermal gravimetric and differential scanning calorimetry, X-ray diffraction, Fourier transform infrared spectroscopy, UV–Vis diffuse reflection spectrum, transmission electron microscopy and ²⁷Al MAS-NMR spectroscopy. Mg_1−xZn_xAl₂O₄ spinel powders with the mean crystallite size of around 11 nm–14 nm were obtained. The crystallinity of the MgAl₂O₄ samples increases with the increase in the calcination temperature. At the same calcination temperature, higher amount of Zn²⁺ substitution leads to the higher level of crystallinity, but has no apparent influence on the mean crystallite size of the samples. The photocatalytic activity of the obtained Mg_1−xZn_xAl₂O₄ spinel nanoparticles was evaluated by monitoring the degradation of methylene blue under UV light. The degradation rates of methylene blue using the MgAl₂O₄ nanoparticles prepared at the calcination temperatures of 700 °C and 800 °C are much higher than those prepared at 900 °C and 1000 °C. The photocatalytic activities of the spinel powders with lower level of Zn²⁺ substitution such as Mg_0.95Zn_0.05Al₂O₄ are inferior to that of MgAl₂O₄. Results of ²⁷Al MAS-NMR spectroscopy analysis and the first principle total density of state calculations reveal that this is probably due to the substitutions of Zn²⁺ decreasing the degree of Al³⁺ ions inversion over the sites of tetrahedral and octahedral coordination. With the increase in the amounts of Zn²⁺ substitution, the effects of Zn²⁺ additions on the photocatalytic activities become gradually predominant, leading to the increases in the degradation rates. The methylene blue degraded by 99% within 4 h using the Mg_0.8Zn_0.2Al₂O₄ spinel powders.     

Synthesis, characterization and self-assemble behavior of chitosan-O-poly(ε-caprolactone)

A facile strategy was proposed for synthesizing chitosan-O-poly(ε-caprolactone) (CS-O-PCL). Stoichiometric sodium dodecyl sulfate-chitosan complex (SCC) which was soluble in common organic solvents was adopted as an intermediate. Regioselective conjugation of PCL onto SCC could be achieved through condensation reaction between isocyanate-terminated PCL and hydroxyl groups of chitosan. The grafting level of PCL could be modulated by varying PCL/SCC weight ratio. SDS was removed from SCC-O-PCL using trihydroxymethylamine (Tris) as a decomplexation agent. The self-assemble behavior of the amphiphilic copolymers was studied by fluorometry, TEM and laser light scattering. The morphology of the CS-O-PCL nanoparticles was found to be dependent on PCL grafting level. Both spherical micelles and vesicle could be formed by dialysis method.     

Synthesis,characterization and visible-light photocatalytic activity of TiO2–SiO2 composite modified with zinc porphyrins

Three types of silica gel supported titanium dioxide particles immobilizing Zn(II) carboxylphenyl porphyrins appending p-CH₃, p-H and p-Cl phenyl substituents (designated as ZnMP–TiO₂–SiO₂, ZnPP–TiO₂–SiO₂ and ZnCP–TiO₂–SiO₂, respectively) have been synthesized and characterized using SEM, XRD, IR, AFS, DRS, UV–Vis, XPS and TG. The photodegradation of α-terpinene in aqueous suspension was used to determine the photocatalytic activity of TiO₂–SiO₂ samples which had been impregnated with Zn(II) porphyrins, as sensitizers. The experimental results confirmed that the photocatalytic activitys of these composites are much higher than those of the nonmodified TiO₂–SiO₂ under visible light irradiation and follow the order of ZnMP–TiO₂–SiO₂ > ZnPP–TiO₂–SiO₂ > ZnCP–TiO₂–SiO₂.     

Synthesis, characterization, and supercapacitive properties of β-Co(OH)2 leaf-like nanostructures

Leaf-like nanostructures of ??-Co(OH)₂ were successfully prepared via galvanostatically cathodic electrodeposition at the current density of 1?mA?cm^?2 from an aqueous 0.005?M Co(NO₃)₂ bath. The bath temperature was fixed at 60?°C. The XRD and FTIR results revealed that the prepared sample has a single phase of the hexagonal brucite-like ??-Co(OH)₂. Morphological characterization by SEM showed that the prepared ??-Co(OH)₂ was composed of discrete leaf-like nanostructures with edge lengths ranging from 250 to 450?nm. The electrochemical performance of the prepared ??-Co(OH)₂ was evaluated using cyclic voltammetry and charge?Cdischarge tests. A maximum specific capacitance of 772.8?F?g^?1 was obtained in aqueous 1?M KOH with the potential range of ?0.3?C0.5?V (vs. Ag/AgCl) at scan rate of 10?mV?s^?1, suggesting the potential application of the prepared nanostructures in electrochemical supercapacitors. Result of this work showed that cathodic electrodeposition can be recognized as a facile method for the preparation of cobalt hydroxide.     

Synthesis, structure and characterization of binuclear copper(Ⅱ) complexes

At room temperature, dibenzoyl peroxide undergoes oxidative addition reaction with metallic copper powder and pyridine N-oxide (triphenylphosphine oxide or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolin) which affords the last products as binuclear copper(II) complexes, [Cu(C5H5NO)-(C6H5COO)2]2(1), [Cu(OPPh3)(C6H5COO)2]2(2) and [Cu(C6H5COO)(C26H2oN2)](3, C26H2oN2 is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolin). The structure of the complexes were characterized by elemental analyses, IR spectra, TG-DTA and magnetic property. Crystals(1) are triclinic, space group P1,a=0.92617(36),b=1.06973(17), c=1.08813(29) nm, a=59.60(2)°, β=74.83(3)°,γ=72.80(2)°, V=0.880 nm3, Dc=1.520 g/cm3, Z=1, R=0.044, Rw=0.048, Mr=805.78, 3477 reflections with I > 3σ(I). Each copper(Ⅱ) ion is coordinated by two bridging bidentate benzoate ligands and one pyridine N-oxide or triphenylphosphine oxide to form dimeric binuclear molecules. The structure of the compound(1) shows a clear centre of symmetry.     

Synthesis and characterization of chloro-bis(quinoline-2-carboxylato-κ2N,O)gallium(III)

The preparation and characterization of a new gallium(III) complex with quinoline-2-carboxylate, of formula [Ga(quin-2-c)₂Cl], are described. The crystal structure of the complex has been determined by X-ray diffraction, crystallizing in monoclinic space group P2₁/n with Ga(III) adopting a distorted tetragonal pyramid. Gallium(III) coordinates two quinoline-2-carboxylates and one chloride with a Cl,N₂,O₂ donor set. In the crystal the 2-D supramolecular structure is generated by weak intermolecular interactions, C–H?···?O, C–H?···?Cl, and C–H?···?π. The cytotoxicity assays against several human cancer cell lines (Du145, A549, MCF-7, A498, HT-29) and against mouse fibroblasts (BALB/3T3) revealed moderate antiproliferative activity of the complex.     

Aurivillius family of layered perovskites,BiREWO6 (RE = La,Pr, Gd,and Dy): Synthesis,characterization, and photocatalytic studies

The present work deals with the synthesis, characterization, and photocatalytic studies of layered perovskites belonging to Aurivillius family. Layered perovskites of various chemical compositions, BiREWO₆ (RE = La, Pr, Gd, and Dy), were synthesized by an ethylene glycol–assisted sol–gel method. These materials were characterized by X-ray diffraction, scanning electron microscopy–energy dispersive spectroscopy (EDS), Fourier transform infrared, Raman, and ultraviolet–visible diffuse reflectance techniques. The composition of all these materials was obtained from EDS. The unit cell lattice parameters were attained from Rietveld refinement program, Fullprof.2k, by refining the d-lines of BiREWO₆. The band gap energy of these samples was obtained from the Kubelka–Munk plot. The photocatalytic activity of all the samples was evaluated by photodegradation of methylene blue. The mechanistic degradation pathway of methylene blue was studied using radical quenchers.     

Synthesis and characterization of polyaniline–zirconium dioxide and polyaniline–cerium dioxide composites with enhanced photocatalytic degradation of rhodamine B dye

For the first time, chloroform and 2-butanol were used as solvent systems for the preparation of ZrO₂–PANI and CeO₂–PANI composites. Solubility of the synthesized composites was studied in chloroform, N-methyl-2-pyrrolidinone (NMP), and in mixture of toluene?+?2-propanol (2:1). XRD and cyclic voltammetry data showed that the ZrO₂–PANI and CeO₂–PANI composites possess both crystalline and amorphous domains indicating some sort of conductivity. TGA results showed that ZrO₂–PANI composite have a better thermal stability than pure PANI; however, CeO₂–PANI composite has lower thermal stability than pure PANI. The conjugated unsaturated structure of PANI is responsible for the enhanced photocatalytic properties of ZrO₂–PANI and CeO₂–PANI. Photocatalytic results showed that, at photolysis time of 60 min, rhodamine B (RhB) dye was degraded up to 34 and 35% by ZrO₂–PANI and CeO₂–PANI, respectively. The degradation products of RhB were quantified by LC–MS and GC–MS, and accordingly, a detailed pathway was proposed.     

Thermal and dielectric characterization of multi-walled carbon nanotubes−thermoplastic polyurethanes composites

Multi-walled carbon nanotubes–thermoplastic polyurethanes composites were characterized by means of differential scanning calorimetry and dielectric relaxation spectroscopy. The composite is characterized by two glass transition temperatures T _g . The T _g associated with the soft segment decreases by increasing of carbon nanotubes content, while carbon nanotubes content has practically no effect on the value of the T _g associated with the hard segments. It was observed that rising the temperature and carbon nanotubes content resulted in the increased of both the dielectric permittivity and the loss factor. The presence of carbon nanotubes produces an enhancement of charge carriers trapping, increasing the electrical conductivity. The electrical conductivity of the composite was found to exhibit an insulator to conductor transition at a carbon nanotubes critical content, i.e., the percolation threshold, near 6 wt %.     

Synthesis, characterization, and reactivity of a novel μ-η2:η2-diselenidodicopper(II) complex

The first μ-η(2):η(2)-diselenidodicopper(II) complex has been obtained in the reaction of a copper(I) complex with N,N',N″-tribenzyl-cis,cis-1,3,5-triaminocyclohexane and elemental selenium. The structure and reactivity of the complex is described.     

Synthesis, characterization, and norbornene polymerization of η-benzylnickel(II) complexes of N-heterocyclic carbenes

Neutral η¹-benzylnickel carbene complexes, [Ni(η¹-CH₂C₆H₅)(IiPr)(PMe₃)(Cl)] (3) (IiPr = 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene) and [Ni(η¹-CH₂C₆H₅)(SIiPr)(PMe₃)(Cl)] (4) (SIiPr = 1,3-bis-(2,6-diisopropylphenyl)imidazolin-2-ylidene), were prepared by the reaction between [Ni(η³-CH₂C₆H₅)(PMe₃)(Cl)] and an equivalent amount of the corresponding free N-heterocyclic carbene. The preparation of η³-benzylnickel carbene complexes, [Ni(η³-CH₂C₆H₅)(IiPr)(Cl)] (5) and [Ni(η³-CH₂C₆H₅)(SIiPr)(Cl)] (6) were carried out by the abstraction of PMe₃ from 3 and 4 by the treatment of B(C₆F₅)₃. The treatment of AgX on 5 and 6 produced the anion-exchanged complexes, [Ni(η³-CH₂C₆H₅)(NHC)(X)] (7, NHC = IiPr, X = O₂CCF₃; 8, NHC = IiPr, X = O₃SCF₃; 9, NHC = SIiPr, X = O₂CCF₃; 10, NHC = SIiPr, X = O₃SCF₃). The solid state structures of 3 and 10 were determined by X-ray crystallography. The η³-benzyl complexes of IiPr (5, 7, and 8) alone, in the absence of any activators such as borate and MAO, showed good catalytic activity towards the vinyl-type norbornene polymerization. The catalyst was thermally robust and the activity increases as the temperature rises to 130 °C.     

Synthesis, characterization and photosensitivity of tetrakis-α-(2-methyl-8-quinolinoxy) metallophthalocyanines

Four amphipathic cobalt(II), nickel(II), copper (II), and zinc(II) coordination compounds of tetrakis-α-(2-methyl-8-quinolinoxy)phthalocyanine are synthesized using “DBU catalytic method”. The titled complexes are characterized by elemental analysis, mass spectra, UV-Vis, and IR spectra. In addition, the rates of photo-generated singlet oxygen and the rate constants of photo-dynamic oxidation of amino-acid substrate by the complexes are measured under the optical excitation at 670 nm, and the relations between their structures and their photosensitivities are discussed. __________ Translated from Acta Chimica Sinica, 2007, 65(16): 1605–1611 [译自: 化学学报]     

Synthesis, characterization, and multielectron reduction chemistry of uranium supported by redox-active α-diimine ligands

Uranium compounds supported by redox-active α-diimine ligands, which have methyl groups on the ligand backbone and bulky mesityl substituents on the nitrogen atoms {(Mes)DAB(Me) = [ArN═C(Me)C(Me)═NAr], where Ar = 2,4,6-trimethylphenyl (Mes)}, are reported. The addition of 2 equiv of (Mes)DAB(Me), 3 equiv of KC(8), and 1 equiv of UI(3)(THF)(4) produced the bis(ligand) species ((Mes)DAB(Me))(2)U(THF) (1). The metallocene derivative, Cp(2)U((Mes)DAB(Me)) (2), was generated by the addition of an equimolar ratio of (Mes)DAB(Me) and KC(8) to Cp(3)U. The bond lengths in the molecular structure of both species confirm that the α-diimine ligands have been doubly reduced to form ene-diamide ligands. Characterization by electronic absorption spectroscopy shows weak, sharp transitions in the near-IR region of the spectrum and, in combination with the crystallographic data, is consistent with the formulation that tetravalent uranium ions are present and supported by ene-diamide ligands. This interpretation was verified by U L(III)-edge X-ray absorption near-edge structure (XANES) spectroscopy and by variable-temperature magnetic measurements. The magnetic data are consistent with singlet ground states at low temperature and variable-temperature dependencies that would be expected for uranium(IV) species. However, both complexes exhibit low magnetic moments at room temperature, with values of 1.91 and 1.79 μ(B) for 1 and 2, respectively. Iodomethane was used to test the reactivity of 1 and 2 for multielectron transfer. While 2 showed no reactivity with CH(3)I, the addition of 2 equiv of iodomethane to 1 resulted in the formation of a uranium(IV) monoiodide species, ((Mes)DAB(Me))((Mes)DAB(Me2))UI {3; (Mes)DAB(Me2) = [ArN═C(Me)C(Me(2))NAr]}, which was characterized by single-crystal X-ray diffraction and U M(4)- and M(5)-edge XANES. Confirmation of the structure was also attained by deuterium labeling studies, which showed that a methyl group was added to the ene-diamide ligand carbon backbone.     

Synthesis,characterization and reactivity of a neutral antimony(Ⅲ) complex

Pincer complexes are widely used in organometallic and coordination chemistry.The role of antimony as a central donor atom in pincer ligands has been extensively explored in recent years.Although phenylenediamine derived PXP(X=B,Al,C,Si,Ge,Sn,N) type ligands exhibit diverse reactivity,analogues species based on antimony have been reported less frequently.Herein,we report a new PSbP complex and evaluate its reactivity.These species will broaden the family of phenylenediamine derived pincer complexes.